Determination of LC₅₀ of Octinoxate (2-ethylhexyl-4-methoxycinnamate) in Artemia salina

UV filters such as octinoxate have become a growing concern due to their widespread presence and accumulation in aquatic systems. These compounds are frequently detected in water bodies as a result of recreational activities such as swimming and wastewater discharge, with the highest reported concentrations found in coastal seawater, reaching up to 390 µg/L. This study evaluated the toxicity of octinoxate, a component in sunscreens and other personal care products, on Artemia salina at the nauplius stage and calculated LC₅₀ values at 24 and 48 hours of exposure. A stock solution of 200 mg/L octinoxate in methanol was used to prepare six dilutions at concentrations of 0.10, 0.30, 0.50, 0.80, 1.00, and 1.50 mg/L. Four six-well plates were used, with each well containing 10 nauplii. A positive control group containing methanol and artificial seawater as well as a negative one containing only artificial seawater were included for comparison. The treatment groups and controls were analyzed in triplicate. All groups were incubated at 28°C, mortality was recorded using a stereomicroscope and morphological effects were analyzed with a digital microscope at 24 and 48 hours. The results showed a concentration-dependent toxic effect in nauplii. The LC₅₀ was 1.200 ± 0.26 mg/L at 24 hours and 0.977 ± 0.41 mg/L at 48 hours, indicating increased toxicity over time. Additionally, morphological abnormalities and erratic swimming behavior were more frequently observed at higher concentrations (1.00 and 1.50 mg/L). No mortality or visible abnormalities were observed in the negative nor positive control group. These findings emphasize the environmental relevance of octinoxate as a widely used organic UV filter and suggest that its continuous release into aquatic systems may contribute to adverse effects on marine organisms.